How was promethium considered a chemical element?

Promethium is one of the most fascinating of all chemical elements. It has never been found on ... By about 1900, most of the chemical elements had been discovered, but a few empty boxes remained on the periodic table. Chemists wondered why ... The smaller atoms are called fission products. read more

Promethium (formerly prometheum) is a chemical element with symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms, a distinction shared with technetium. read more

Promethium is one of the most fascinating of all chemical elements. It has never been found on the Earth's surface. Scientists know of it only because it can be prepared artificially in particle accelerators ("atom smashers") and in other unusual reactions. read more